1. Field of the Invention
The present invention relates generally to microdevices and more particularly to microscopic and nanoscopic actuators.
2. Description of the Prior Art
Stimuli responsive polymers (SRPs) comprise a class of synthetic, naturally occurring and semi-synthetic polymers, which exhibit discrete rapid and reversible changes in conformation as a response to environmental stimuli. These stimuli may include temperature, pH, ionic strength, electrical potential and light. Some of the most studied of these so-called smart polymers are hydrogels which change their water content and excluded volume, in response to temperature. Various types of stimuli responsive polymers in ensembles to control the permeability of solutes and fluids through membranes or through bulk materials have been described. In recent years, these types of polymers have been developed for a variety of different applications including drug delivery, control of protein activity and most interestingly, systems that mimic natural cellular components, such as cellular membranes and secretory granules. Smart polymers that have found use in biotechnology and medicine have been described by I Yu Galaev in Russian Chemical Reviews 64: 471-489 (1995) and A. S. Hoffman in Clinical Chemistry 46:1478-1486 (2000).
In recent years with the advent of high throughput technologies in use in the pharmaceutical and biotechnology industries, a need for microscopic and nanoscopic molecular actuators has arisen. However, to date there is no stimuli responsive polymer described which can individually serve as microscopic and or nanoscopic molecular actuator to control the transport of other chemical species through molecular-sized pores in a porous material. Hence there is a current unmet need for materials that are able to provide nanoscopic actuation of individual stimuli responsive polymers within or on the framework material. Such materials would ideally be able to address the current needs of: (1) new, inexpensive valving and pumping strategies for control of liquid flow in nanofluidic systems; (2) rapid, energy-efficient, inexpensive chemical separation strategies; based on and (3) reversible affinity matrices for chemical sensing and chemical separations; (4) micropatterning of chemical and biological species; (5) prevention and release of biofouling; (6) optical switching; and (7) tissue engineering.
It is therefore an object of the present invention to provide a new class of valves made of hybrid materials that use dispersed molecular switches as nanoscopic actuators that individually control the transport of other chemical species through molecular-sized pores in a porous material.
It is a further object to provide a very sensitive mechanism of control of transport through valves by using the individual, molecular actuators to control the permeation and or absorption, by limiting pore size and chemistry of a membrane, thin film or particle constructed from the hybrid material.
It is yet another object to provide a means for selective transport and or adsorption of different molecular species through valves by using size exclusion and/or polarity differences.
It is yet another object to provide a specificity of transport through a molecular actuator that is based on a reversible size, shape or chemical change in the active component of the hybrid material or materials that are used to make the molecular actuator.
In a first broad aspect the present invention provides a hybrid material comprising: at least one actuator, the at least one actuator comprising a stimuli responsive polymer that has first conformation in a first environment and a second conformation in a second environment; and a porous framework material for supporting the at least one actuator.
In a second broad aspect, the present invention provides a method for forming a hybrid material comprising: providing at least one actuator, the at least one actuator comprising an stimuli responsive polymer that has first conformation in a first environment and a second conformation in a second environment; and immobilizing the actuator on a framework material.
In a third broad aspect the present invention provides a valve comprising: at least one channel; and a hybrid material located in the channel comprising: at least one actuator, the at least one actuator comprising a stimuli responsive polymer that has first conformation in a first environment and a second conformation in a second environment; and a porous framework material for supporting the at least one actuator.
In a fourth broad aspect the present invention provides a differential sieve comprising: at least one channel; at least two actuators mounted in sequence in the channel, each of the actuators comprising different stimuli responsive polymer; and means for actuating each of the at least two actuators to form at least two different sized passageways through the channel.
In a fifth broad aspect the present invention provides a peristaltic pump comprising: at least one channel; at least two actuators mounted in sequence in the channel, each of the actuators comprising at least one stimuli responsive polymer; and means for actuating each of the at least two actuators in sequence to pump a liquid present in the channel through the channel.
Other objects and features of the present invention will be apparent from the following detailed description of the preferred embodiment.